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March 27, 2007
Spring Arrives
Like most Michigan residents, I greatly anticipate the arrival of spring weather. Much as I like the change of seasons, the icy grip of winter loses its appeal by the end of February. The incremental warming and lengthening days that lead to the vernal equinox are often overshadowed by the whims of weather, as we are more likley to have cold and gloomy days as anything around March 21. Once the evening temperatures ameliorate and begin to be about 10 degrees above freezing, I start to see some fluttering shapes at the backyard light. Perhaps, instead of the crocuses bursting forth to announce spring's arrival, we should contemplate the Spring Cankerworm as a harbinger of warmer days.
Paleacrita vernata (Peck) is the latin name for the Spring Cankerworm, a member of the geometrid moth family that includes hundreds of species that are mostly benign, and some are even quite pretty. The larvae are called inchworms.
P. vernata, on the other hand, isn't exactly pretty, but it does have an interesting biology. Females are wingless, which means that the males are the moths that we see fluttering around the porch light. Males find the females at night by following a pheromone plume emitted by the females. After mating, the female lays 100 or more eggs on a flap of bark, or bark crevices. The larvae hatch in early May, and become full-grown within a month. Then, they drop to the soil and remain there until late winter, when they pupate, and emerge in March.
Spring Cankerworm rarely becomes a serious defoliator, but there have been sporadic localized outbreaks in the past. It's usually held in check by natural predators and parasites, but when they become a problem, one can place sticky bands around tree trunks to prevent female moths from climbing up the trunk to lay eggs.
So, look upon the Spring Cankerworm as the insect version of the American Robin.
Posted by mfobrien at 09:55 AM | Comments (0)